1. Field of the Invention
The present invention relates to a semiconductor device that suppresses a surge voltage.
2. Description of the Background Art
In an inverter semiconductor module (inverter circuit) or a chopper circuit using a switching element of a high switching speed such as an IGBT, turning the switching element off generates rapid current change. As a result, a high voltage (turn-off surge voltage) is generated in response to the floating inductance of a main circuit. Meanwhile, even in the presence of a freewheeling diode (recovery diode), a high voltage (recovery surge voltage) is still generated based on the same principles when the freewheeling diode is turned off.
So, in order to maintain the safe operating area (SOA) of a switching element, a snubber circuit for reducing a surge voltage to be generated during turn-off is provided in an inverter circuit having an inverter bridge or a chopper circuit. Such a snubber circuit is disclosed for example in Japanese Patent Publication No. 4323073.
In a conventional semiconductor device with a snubber circuit, the snubber circuit converts a surge voltage to Joule heat, and dissipates the heat. In other word, part of electric power energy supplied is gone to waste uselessly, so it is regarded as undesirable in terms of energy saving.